Engine overheated Hi, i have replaced the thermostat and housing on me 728i which overheated and i had to get towed home. I cannot stop it overheating after i have gone a couple of miles. Can anyone suggest anything as i have not got a manual to work with.

Hello, There are many things that can cause this problem. It could be anything from a blown head gasket to a water pump. If you want to eliminate the water pump, take the thermostat back out and leave out, start motor, and see if you have a good coolant flow from water pump. Also, ck your fan clutch. This won't necessarily cause it to overheat at road speed but at slow speed or idle it could. There is also the possibility that your radiator is stopped up. There is something else, although rare, I have seen happen. Check the small coolant return hose at the radiator to make sure something hasn't blocked the small plastic nipple. If this is blocked, coolant will not circulate. Check your engine oil for any kinds of water contamination, check your plugs for water, if you have access to a coolant pressure tester, pressurize cooling system, remove spark plugs, let stand for at least an hour, then turn engine over and see if any coolant comes out. This may give you an indication that your head gasket is blown. I hope this helps.CYA, Gator241

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Assuming you replaced the radiator with new or refurbished. You probably need to replace the thermostat. It is usually located on the engine block in a housing at the end of the top radiator hose. Probably just two bolts in the thermostat housing.

It is not recomended to flat tow your expedition with the engine off and driveshaft in. The oiling system in your transmission runs off of the engine. You can tow short distances but the transmission components will be turning without fresh fluid being moved through them. This will cause exessive wear due to the fluid overheating and losing its ability to lubricate properly. You can flat tow unlimited distances with the engine ideling or the driveshaft removed. if you chose to tow with the engine running you should stop often to make sure you are not overheating the engine. You may not get enough air flow to the radiator while the expedition is behind your motor home.

Well the alternator would have nothing to do with the overheating! If the alt went bad, you'd be having electrical issues, not cooling issues. Why would you change an Alternator if it was overheating? Was somthing else happening at the time to make you think you had a electrical issue?

The thermostat could be stuck closed or the water pump failed, both common issue, sound like somthing is causing the engine to either run hot, or not cool properly.

Once the engine has overheated sadly the damage is done, you could have simply cooked a sensor,or it could be as bad as you could have warped the block or head, or one of a number of other things!

Hot engines are hard to start, you should let them compleatly cool down first! In fact you should have either checked the car out or had someone check it out before attempting to start or drive it again, this is why god created tow trucks! A $50 towing charge or a $5000 engine repair bill, I know which one I would choose!

did you have the heads worked at a machine shop (pressure tested, valves seals replaced and ground , and milled )? also how many mies are on the engine? the ticking noise very well could be timing chain noise. as for the overheating did you check the water pump to make sure your getting proper circulation. you can test it by removing one heater hose from the intake then start the engine. if the pump is good then water should spray out of the hose if the pump is weak then the water may trickle out.

I think at the minimum you have a blown head gasket. I am guessing you drove the car a considerable distance with not enough coolant and now you may have done extensive damage to the engine. I am guessing that if the engine still cranks, than the head is warped to an extent where there is not enough compression to support combustion.

The thermostat and water pump are both common failure points on BMW 6-cyl engines of this era.
I would recommend checking the thermostat first, then moving on to the water pump.
If the vehicle has overheated several times, you may need to remove the cylinder head and have it checked for warp.

This sounds like a faulty thermostat. The fact that running the heater helps with the overheating is a common symptom of a faulty thermostat. Just follow the top radiator hose to where it hooks on the engine. The thermostat is located inside the housing that the hose attaches to. A thermostat is relatively inexpensive and easy to replace. Just make sure that all old gasket material is removed from the housing before installing new gasket and thermostat. Also, don't overtighten the bolts, the housing can be easily compromised if the bolts are overtightened. Hope this helped and best wishes.

You need to have a coolant flush done to your engine. Overheating the coolant will brake down the properties of the antifreeze. Have a garage flush your cooling system thorougly and replace the old coolant with the proper OEM coolant. You will also need to replace your thermostat as overheating this unit will have damaged the thermostat. Replace the rad cap while your at it because there is a spring that regulates your cooling system pressure and it will now be weakened.
Just a note, Overheating your engine will cause damage to your engine. If the temperature gauge is near the red zone, stop the engine before any major damage can occure.